Tetiary-alkylamino-lower-acyl-xylidide local anaesthetics

ABSTRACT

Tertiary-alkylamino-lower acyl-xylidides have unusually long lasting local anaesthetic effect or high local anaesthetic activity while also having a satisfactory low level of tissue irritation and a satisfactory low acute toxicity. Combinations of such local anaesthetics with the biotoxins tetrodotoxin or saxitoxin are disclosed. Novel tertiary alkyl secondary amines, and methods for preparing such local anaesthetics and amines are also disclosed.

United States Patent [191 Adams et al.

[ Dec. 9, 1975 TERTIARY-ALKYLAMINO-LOWER-ACYL- XYLIDIDE LOCALANAESTHETICS [75] Inventors: Herbert H. F. Adams, Westboro;

Jon C. Anderson, Wyckoff, both of N.J.; Murray R. Blair, Jr., Sudbury,Mass; Robert L. DiRubio, Paxton, Mass; Berti! H. Takman, Worcester,Mass.

[73] Assignee: Astra Pharmaceutical Products, Inc.,

Worcester, Mass.

[22] Filed: June 12, 1973 [21] Appl. No.: 369,146

Related US. Application Data [63] Continuation-impart of Ser. Nos.230,114, Feb. 28, 1972, abandoned, and Ser. No. 325,378, Jan. 22, 1973,abandoned.

[52] US. Cl. 260/562 B; 424/324 [51] Int. Cl. C07C 103/34 [58] Field ofSearch 260/562 [56] References Cited FOREIGN PATENTS OR APPLICATIONS771,151 3/1957 United Kingdom 260/562 307,799 6/1955 Switzerland 260/562OTHER PUBLICATIONS Epstein et al., J. Amer. Phann. Assoc., Vol. 49, p,

Lofgren et al., Acta Chemica Scand., Vol. 11, p. 1724-1737 (1957).

Primary ExaminerHarry l. Moatz Attorney, Agent, or Firm-Brumbaugh,Graves, Donohue & Raymond [57] ABSTRACT 4 Claims, No DrawingsTERTIARY-ALKYLAMINO-LOWER-ACYL- XYLI-DIDE LOCAL ANAESTHETICS Thisapplication is a continuation-in-part of our copending applications US.patent application Ser. No. 230,114 filed Feb. 28, 1972, now abandoned,and Ser. No. 325,378 filed Jan. 22, 1973, now'abandoned.

The present invention relates to tertiary-alkylaminolower acyl-xylididelocal anaesthetic compounds.

Two acylxylidide local anaesthetic compounds which are commerciallyavailable are N-n-butylpipecolyl-2,6- xylidide or bupivacaine sold underthe trademark Marcaine having the structural formula CH3 cnzcnzcn zcna Hi N NH-"C and diethylaminoaceto-Z,6'xylidide or w-diethylamino-2,6-dimethyl-acetanilide or lidocaine sold under the trademark Xylocainehaving the structural formula However, while bupivacaine or Marcaine isa long lasting local anaesthetic, it has the drawback of being moreirritating to tissue than lidocaine and while lidocaine or Xylocaine isnot irritating to tissue, it has the drawback of not being a longlasting local anaesthetic.

Other local anaesthetics which are commercially available includea-propylaminopropiono-2-toluidide or prilocaine sold under the trademarkCitanest; apyrrolidinoaceto-Z,6-xylidide or pyrrocaine sold under thetrademarks Endocaine" and Dynacaine; and N-methylpipecolyl-Z,6-xylidideor mepivacaine sold under the trademark Carbocaine. However, these localanaesthetics are of short action.

It is, therefore, the principal object of the present invention toprovide compounds which have an unusually long lasting local anaestheticeffect or high local anaesthetic activity while also having asatisfactory low level of tissue irritation and a satisfactory low acutetoxicity.

The local anaesthetic compounds of the present invention aretertiary-alkylamino-acetoxylidides or -propionoxylidides. Morespecifically, these compounds are as follows:

A. 2-( terL-butylamino )-2 ',6-acetoxylidide B.2-(tert.-butylamino)-2,6-propionoxylidide C.2-(N-ethyl-tert.-amylamino)-2',6'-acetoxylidide CHzCH-2CH3 H CH 3 E.2-(N-n-butyl-te1t. butylamino)-2',6-acet0xylidide F. 2-(N-tert.-amylamino)-2 ',6 '-acetoxylidide These compounds may besynthesized or prepared in accordance with the procedures given in theexamples 1 and illustrations set forth hereinafter.

These procedures or processes may be illustrated by the followingpartial equations:

IA. Preparation of 2-(tert.-butylamino )-2,6'-acetoxylidide Instead ofchloro acetyl xylidide, the corresponding bromoor iodocompound may beused. If desired, Nal, KI or a suitably chosen quaternary ammoniumiodide may be present during the reaction when the chloroorbromocompound is used.

IB. Preparation of 2-(tert.-butylamino)-2,6-propionoxylidide Thiscompound may be prepared by the procedure described in IA, using thecorresponding 2-halo propionoxylidide, instead of the Z-haloacetoxylidide, as the starting material.

II. Preparation of 2-( N-e thyl-tert.-amylamino )-2 ',6 '-acetoxylidideInstead of diethyl sulfate, other ethylating agents may be used, such asethyl iodide or.ethyl bromide.

The compound may also be made by the reaction described below (IIIA),using CH CI-IO as the starting material instead of CH CH CI-IO.

III. Preparation of 2-(Nn-propyl-tert.-amylamino)-2',6'-acetoxylidideNH-C-CHJ HN CH3 CH CH l... C H 3 CH CH CH H. cu

Instead of the iodo-acetyl xylidide the corresponding chloroorbromocompound may be used as a starting material, in which case asuitable alkali metal or quaternary ammonium iodide will be used topromote the reaction, as in 11 above.

a CH preferably with a suitable acid acceptor. Instead of npropyliodide, n-propyl bromide may be used.

Preparation of the sec. amines, N-ethyl-tert.-amyl amine, andN-n"-propyl-tert.-amyl amine In addition to the methods described above,these' compounds, which are intermediate compounds in the preparation ofthe local anaesthetic compounds of the invention, may be made asfollows.

NH tert. C H,, suitable ethylating agent tert. C H

suitable propylating agent [c.g. n-C H,1 or nC H Br) NH tert. C H

tert. C H

. e.g., the hydrochlorides, tartrates and citrates. Anaestheticcompounds C and D above provide anaesthesia of significantly longerduration than compounds A and B. Compounds A and B could be used forshort procedures in surgery, e.g., such as those requiring infiltrationanaesthesia, minor nerve blocks, and certain forms of regionalanaesthesia. Compounds C and D could be used in surgery when longerduration of anaesthesia is desired. Because of the possibility ofvarying the concentration and dose of the agents it is however, possibleto obtain satisfactory anaesthesia outside of the range exemplifiedabove with both groups of agents. The compounds A, B, C, D, E and F,moreover when used in combination with biotoxins tetrodotoxin orsaxitoxin produce long lasting local anaesthetic effect.

The invention will be further illustrated by the following examples:

EXAMPLE 1 This example illustrates the preparation of 2-(tert.-butylamino)-2',6-acetoxylidide.

To 1 liter of absolute alcohol, 120 g. (0.608 mole)2-chloro-2,6-acetoxylidide and 272.2 g. (3.108 mole) tert.-butylaminewere added. The reaction mixture was heated at C. for 18 hours in anautoclave. After cooling the solvent was evaporated in vacuo. The creamcolored residue was dried (vacuum desiccator) and then stirred inbenzene for 30 minutes. The undissolved material (tert.-butylammoniumchloride).was collected and discarded. The supernatant was evaporated invacuo leaving a yellowish residue which was collected, dried, andrecrystallized twice from petroleum ether (b.p. 60-1 10C.). An 85.9%yield of a white crystalline material, m.p. 8788.5C., was obtained.

Anal. Calcd. for C H- N O: C, 71.75; H, 9.46. Found: C, 71.62; H. 9.43.Ir (KBr disc, base) 3318 (m;

7 sec. amine, 3255 (m; amide, NH-stretch), 1673 (s; amide l), 1592 (w;aromatic), 1495 (s; amide 11), 1385 (w) and 1370 (w) (methyl CHbending), 778 (s; 3 adjacent out of plane aromatic H) cm CH3 lNH-C-CH2--NCCH3 EXAMPLE 2 This example illustrates the preparation of2-(tert.- amylamino)-2,6-acetoxylidide, and the preparation of 2-(Nethyl-tert.-amylamino )-2 ',6 '-acetoxylidide from 2-( tert.-amylamino)-2 ,6 '-acetoxylidide.

2-(tert.-amylamino )-2',6'acetoxylidide To 400 ml. of anhydrous benzene,18.9 g. (0.0956 mole) 2- chloro-2,6-acetoxylidide, 20 g. (0.2295 mole)tert. amylamine and l g. of sodium iodide were added. The reactionmixture was heated at 100C. for 36 hours in an autoclave. A precipitatewas collected and discarded. The resulting filtrate was stripped ofsolvent and the yellow oily residue was dissolved in ether, theundissolved material being collected and discarded. After drying (Na SOthe ether was stripped off in vacuo leaving a yellow oily liquid whichwas taken up in dilute hydrochloric acid (final pH 2). The acidic aqueous phase was washed several times with ether, basified to pH 9.5 withconcentrated ammonia, and the precipitated base extracted with ether(4X100 ml.). The ether extract was dried (Na S and evaporated in vacuoleaving a yellow oily residue which was distilled in vacuo (b.p. 150C.,0.05 mm.) to give under refrigeration, 16.6 g. ofa white solid, mp.54-55.5C. (The hydrochloride was also prepared and recrystallized fromacetonitrile, mp. 209-21 1C.).

Anal. Calcd. for C I-1 N 01 C, 72.54; H, 9.74; N, 11.28. Found: C,72.32; H, 9.98; N, 11.34. l.r. (KBr disc, hydrochloride) 3150-3120 (m-s;amide, NH stretch); 2710 (s), 2620 (m), 2580(m), 2440 (m), and 2417(m-w) (NH stretch); 1665 (s; amide I), 1590 (mw,' aromatic), 1542 (s;amide I1), 1393 and 1375 (s-m; methyl CH bending), 775 (s-m; 3 adjacentout of plane aromatic H) cm.

2-(N-ethyl-tert.-amylamino)-2',6-acetoxylidide To 46.52 g. (0.3017 mole)diethyl sulfate, 10.7 g. (0.0431 mole) 2-(tert.-amylamino)-2',6-acetoxylidide was added, and the mixture was heated for 4 hours and20 minutes at 100C. After cooling the reaction mixture was taken up inhydrochloric acid (final pH 2). The mixture was washed with ether(2X100m1.) and the aqueous solution basified to pH 9 with concentratedammonia followed by extractions with ether (5X75 ml.). The combinedether extracts were dried (Na SO and the ether removed in vacuo leavinga white solid residue. The residue was recrystallized three times fromethanol/H O. A 37.1% yield of a white crystalline material, m.p.1ll.5113.5C., was obtained.

Anal. Calcd. for C H N O: C, 73.87; H, 10.21; N, 10.14. Found: C, 73.94;H, 9.94; N, 10.21. IR. (KBr disc, base) 3262 (s; amide, NH stretch),1655 (s; amide I) 1590 (w; aromatic), 1498 (s; amide II), 1385 and 1375(w; methyl CH bending), 766 (s; 3 adjacent out of plane aromatic H) cm.

CH3 CH EXAMPLE 3 This example illustrates the preparation of2-(N-npropyl-tert.-amylamino)-2,6-acetoxylidide fromN-npropyl-tert.-amylamine.

N-n-propyl-tert.-amylamine A suspension of 1.0 g.

of 10% palladium on charcoal in ml. absolute alcohol was shaken withhydrogen until more hydrogen was absorbed. To the catalyst mixture, 30g. (0.3442 mole) tert.-amylamine was added followed by a solution of 18g. (0.3098 mole) propionaldehyde in 50 ml. of absolute alcohol. All ofthe above ingredients were cooled in an ice bath before combining. Afterwarming to room temperature, the reaction mixture was shaken withhydrogen at an initial pressure of 59 psi for 10 hours, by which timethe theoretical amount of hydrogen was absorbed. The catalyst wasseparated by filtration, washed with ethanol, and 40 ml. of concentratedhydrochloric acid was added to the combined filtrate. The solution wasbrought to dryness by evaporation in vacuo. The dried product wasdissolved in 250 ml. distilled water and g. of 50% sodium hydroxide wasadded slowly with cooling to liberate the amine. The mixture wasextracted with ether (3X200 ml.) and the combined ether extracts weredried over anhydrous sodium sulphate. The dried extract was distilledthrough a 300 mm. column packed with /811'1Cl1 1D glass helices yielding26.7 g. 66.7%) on N-n-propyl-tert.-amylamine, b.p. l36.5-137.5C.(atmospheric pressure), n 1.4106.

Anal. Calcd. for C H N: C, 74.34; H, 14.82; N, 10.84. Found: C, 74.76;H, 15.16; N, 10.96.

HN CH1,

9 2-(N-n-propyl-tert.-amylamino)-2',6' -acetoxylidide To 150 ml.benzene, g. (0.0346 mole) 2-iodo-2',- 6' acetoxylidide and 11.18 g.(0.0865 mole) N-n-propyl-tert.-amylamine were added. The reactionmixture was refluxed for 29 hours. After cooling the reaction mixturewas stripped of benzene and unreacted amine in vacuo. The resultingsemisolid material was treated with anhydrous ether. The undissolvedmaterial was filtered off and discarded and the ether was evaporated invacuo. The yellow, waxy material was recrystallized twice fromethanol/water and twice from acetone/water. A 49.4% yield of whitecrystalline material, m.p. 96.5-97.5C., was obtained.

Anal. Calcd. forC H N oi, C, 74,43; H, 10.41; N, 9.65. Found: C, 74.4;H, 10.35; N, 9.59. l.r. (KBr disc, base) 3240 (m; amide NH stretch),1665 (s; amide l), 1495 (s; amide 11), 1385 and 1370 (w, methyl CHbending), 766 (s; 3 adjacent out of plane aromatic H) cm. Ahydrochloride was prepared from the base. It was obtained as a stablemonohydrate melting at l81.2l82.8C.

Anal. Calcd. for C H ,C1N O H 0: H 0, 5.22. Found: (Karl Fischer) H O,5.21.

EXAMPLE 4 This example illustrates the preparation of 2-tert.-butylamino)-2,6-propionoxylidide.

To 300 ml. of absolute alcohol, 38.42 g. (0.15 mole) of2-bromo-2,6"propionoxylidide and 54.85 g. (0.75 mole) of tertiarybutylamine were added. The reaction mixture was heated at 100C. for 18hours in an autoclave. After cooling, the alcohol and unreacted aminewere removed by distillation in vacuo. The residue was dissolved inether and concentrated NH OH was added. Undissolved material(tertiarybutylammonium bromide) was collected and discarded. The twophase supernatant was separated and the basic aqueous phase discarded.The ether phase was dried over anhydrous Na SO and subsequently removedin vacuo. The cream colored residue was stirred in benzene for 30minutes. Undissolved material (tertiarybutylammonium bromide) wascollected and discarded. Evapo ration of the benzene in vacuo gave acream colored residue which collected, dried and recrystallized threetimes from petroleum ether (b.p. 601l0C.). A

54.1% yield of white crystalline material, m.p.

124.5126C., was obtained.

Anal. Calcd. for: C H N O: Calcd.: C, 72.54; H, 9.74; N, 11.28. Found:C, 72.62; H, 9.83; N, 11.34.

0 H ca, NH cu 1L C/CH CH3 CH3 EXAMPLE 5 This example illustrates thepreparation of N-npropyl-tert.-amylamine.

A mixture of 2 moles of tert. amylamine and 1 mole of l-bromo-propane isrefluxed for 6 hours. The reaction mixture is cooled and kept at +4C.for 1 hour. After filtering, the filtrate is fractionated by columndistillation and the colorless, clear fraction boiling between 136l38C.is collected.

EXAMPLE 6 tracted twice with ether. The ether extract is discarded andthe aqueous phase is made alkaline by the addition of concentratedammonia to a Ph of 9-10 whereafter it is extracted several times withether. This ether extract is dried (K CO and, after filtering, the etheris removed in vacuo. The residue is recrystallized from ethanol/water.

EXAMPLE 7 1n a manner similar to the preparation of 2-(tert.-amylamino)-2,6'-acetoxylidide of Example 2, 2- chloro-2,6'-acetoxylidideis reacted with N-n-propyltert.-amylamine in the presence of sodiumiodide to fonn Z-(N-n-propyl-tert. amylamino)-2,6'-acetoxylidide. Theresulting reaction mixture is worked up as described in Example 3 forthis compound.

EXAMPLE 8 This example illustrates the preparation of2-[N-(nbutyl)-tert. -butylaminol]-2,6'-acetoxylidide.

A mixture of 600 g. 2-iodo-2',6-acetoxylidide, 643

-g. N-(n-butyl)-tert.-butylamine, and 4.5 liter of benzene were heatedto reflux in a flask equipped with a machanical stirrer and a refluxcondenser for l5-l6 hours. The compound N-(n-butyl)-tert.-butylamine isdescribed by J. N. Tilley and A. A. R. Sayigh in J. Org. Chem. 28, 2076(1963). It is prepared analogously to N-propy'terL-amylamine of Example3 from nbutyraldehyde and tert.-butylamine. After cooling theprecipitate of N-(n-butyl)-tert.-butylammonium iodide was filtered off(dry weight 482 g.). The filtrate was extracted with 4 M hydrochloricacid. (The acid extract can be filtered and washed with ether at thispoint). The acid extract was made alkaline with 7 M sodium hydroxide.The precipitate was taken up in methylene chloride and the alkalinesolution was extracted with the same solvent. The methylene chloridesolutions (combined) were dried (Na SO after filtered, and evaporated.The residue was recrystallized from a mixture of acetone and water (7-8:l) and a yield of 414 g. was obtained, m.p. l40-l40.5.

Calcd. for C H N O: C, 74.4; H, 10.4; N, 9.65. Found: C, 74.6; H, 10.5;N, 9.49.

B is 2-(tert.-butylamino)-2,6-propionoxylidide.

C is 2( N-ethyl-tert.-amylamino)-2,6-acetoxylidide.

D is 2-(N-n-propyl-tert.-amylamino)-2,6-acetoxylidide.

E is 2-(N-n-butyl-tert.-butylamino)-2,6'-acetoxylide.

F is 2-(N-tert.-amylamino)-2,6'-acetoxylidide.

X is the prior art compound N-n-butylpipecolyl-2,6-

xylidide, i.e., bupivacaine or Marcaine.

Y is the prior art compound diethylaminoaceto-2,6-

xylide, i.e., lidocaine or Xylocaine.

Tables I, II and III contain comparative data on the 3 CHZCHzCHzCHaduration of several of these local anaesthetic compounds, Table IVcontains comparative data on the ef- NHCOCH N 15 feet on the actionpotential of the isolated frog sciatic nerve preparatron of some ofthese local anaesthetrc C (CHM compounds while Table V containscomparative data on the acute toxrcrty of several of the localanaesthetrc CH 70 compounds. Table VI contains the data from tests on 3peridural anaesthesia in the dog for compound D. Table VII contains datafrom tests run on compound B on rat sciatic nerve blocks, guinea pigwheals, irritation on the rabbit back, and acute toxicity in mice. TheCOmPOUnd y y Irritation indices -reported in Table VI are deter-2',6'-acetoxylidide may also be prepared by the proce- 25 i d i h f ll imanner; dure described in Example 6 from Wheals are made on the shavedbacks of albino rabbUty1amiI10)-2',6l"acetoxylldide and y bromidebits byintraderrnal injection of aqueous solutions of the It y also be P p ythe Procedure described agents. Twenty-four hours later each wheal isgraded in Example 7 from Z'ChIOYO-Z',6"aCet0Xylidide and for: presenceand severity of erythema, presence and n-butyl-tert.-butylamine. 3Oseverity of edema, and presence or absence of necrotic In the tablespresented below the following code destissue in the wheal. The gradingis done on an arbitrary ignations have been used: numerical scale, and amean irritation index is calcu- A is 2-tert.butylamin0)-2.6'-acetoxylidide. lated for all wheals at a givenconcentration.

TABLE I Rat Sciatic Nerve Blocks* Duration in Minutes Standard Deviation7c Conc. as base A C D X Y 0.125 88:11 115:16 124150 121132 0.25 173120159130 157130 175:16 102115 0.5 184:3? l60:l0 217125*** 212134 1231101.0 250 1 32 20s 1 35 8-27 days 213 102 1 39 2.0 270 1 28 l-8 days 13-30days I85 1 23 All solutions contained l:lO0.000 epinephrine.

*Test method given in Truunt. A.P.: Arch Int. Pharrnacodyn. l l5:483-497 (1958). which is incorporated by reference herein.

"Mean of 3; 7 blocked between 5 and 22 hours.

*Mean of 3'. 2 blocked lO-l3 days.

TABLE II Guinea Pig lntradermal Wheals* Duration in Minutes StandardDeviation All solutions contained l:l00,000 epinephrine.

Test method given in Bulhr'mg. Eyand Wajda. It: J, Pharmacol. Exp.Therupr 85: 78-84 1 W451 which is incorporated by reference herein.

TABLE I11 TABLE VI! Peridural Anaesthesia in the Cat* Duration of Blockof Support of Weight in Minutes i Standard Deviation Compound B:2-(Tert. butylamino)-2',6'propionoxylidide Local Anaesthetic and AcuteToxicity Testing graionc. A C X Y 5 V Rat Seiatic* I ConcentrationDuration Minutes Frequency 0.5 136 t 30 1.0 54 i 9 220 i 64 296 i 77**32E; 2.0 104:29 298-:56*** 88:10 1 12415 10/10 All solutions containedl:l00,000 epinephrine. 1 144 I 9 10/10 Test method given in Duce, B.R..Zelechowski. 14.. Camougis, G. and Smith. 20% 164 i 10 0,10 E.R.: Brit.J. Anaesth. 411579-58 (1969). which is incorporated by reference GuineaPig wheal* herein. Concentration it: Duration Minutes Frequency Toxiceffects observed at this concentration. 7 *Mean of 3 animals; 1 blocked7 hours. 25% 139 i 24 12/12 .5% 160:43 12/12 TABLE IV 15 1.0% 18413612/12 In vitro Studies on Frog Sciatic Nerve Block C t Back GreatestDepth of Average time for 80% once m a "lumen ndex Concn. Block ofaction recovery of action 5% 0 Compound mM potential) potential (min) 31 0 2.0% .5 C 77 29 2 2 22 22 20 Y 20 46 14 61 (45-78 mg/kg LP.

"Solutions contained l:l00.000 epinephrine T V "Depression. ataxia, lossof fighting reflex in some animals at this concentration.

Acute Toxicity in Female Mice Compound LB and 95% Fieller ConfidenceLimits: mg/kg as Base 25 lntraperitoneal (1.1.) Intravenous SubcutaneousA 119(92-136) 35.4(312-41) l4l(l2l-l62) C 81(62-132) 7.4(6.5-8.4) D39(1062) 6.8(6.07.8) 109(78-143) X 40(28-56) 6.4(5.5-7.3) (38-54) Y105(93-132) 19.5( 18-24) 211(183-256) 30 Solutions did not containepinephrine.

TABLE VIII Formulations for 0.25%, 0.50%, 1.00%, 1.50%. and 2.00%Compound D:HC1 solutions for injection containing l:200.000 epinephrineare given below.

' mg./ml.

Compound DZHCl H O 2.64 5.28 10.55 15.82 21.10 Sodium chloride, USPXVIII 8.60 8.20 7.30 6.40 5.60 Epinephrine, USP XVlll 0.005 0.005 0.0050.005 0.005 Sodium metabisulfite 0.50 0.50 0.50 0.50 0.50 Water forinjection, USP XVIII qs ad 1.0 m1.

Indicates percent anhydrous Compound DzHCl TABLE VI In Table IX data arepresented showing the duration Pcridural Anaesthesia in the of blocl ageofi' rat sciatic nerves by compound E in con- Compound D centrations of-0.25l .0% w/v tested by the same Cmcenmm vlume (mm) method as used forthe workrepotted in Table I. Fre- (ml) Digital Scrotal Pain Painquencies and durations were good.

Epinephrine l:l00.()()(l used in all solutions. The values l'or thedurations are mean values and the ranges are given in parenthe- Method:Mature male beagles are surgically prepared by implantation of a cunnulainto a lumbar vertebra so that drug solutions may be administered intothe pcridural space. After administration of local anaestheticsolutions. the animals are examined at intervals for duration of loss ofpain in the scrotal area and in the digits of the hind lim Response toand awareness of pain stimuli in scrotal areas is a test for anaestheticblock in spinal roots L3-4 and 51-2-3. These roots are the furthestremoved from the point of injection (L6) and. therefore. least likely tobe tllTCCILtl hy the anaesthetic. Return of response to pain in thescrotum is often the first sign of recovery and indicates recessionofunacsthcsia to at least 1.4 antcriorly and S2 posteriorly.

Test method: See Table I.

Compound E was also tested for toxicity in mice, rats, and guinea pigs.In mice the'I.P. toxicity (LD was 284 (21853l) mg/kg. In the rat,subcutaneous toxicity was 1068 (813-4507) mg/kg. In guinea pigs testedsubcutaneously all animals survived 646 mg/kg.

The compounds of the present invention are also useful in combinationwith the known biotoxins, tetrodotoxin, desoxytetrodotoxin and Saxitoxinas described and claimed in the copending application of Adams andTakman, Ser. No. 369,202 filed June 12, 1973 which is acontinuation-in-part of application Ser. No. 206,181 filed Dec. 8, 1971and in the copending application of Adams and Takman Ser. No. 369,147filed June 12, 1973 which is a continuation-in-part of Ser. No. 206,182filed Dec. 8, 1971, the disclosures of which are incorporated herein byreference.

The following Table X gives the results of tests on the anaestheticeffect of various compositions of the aminoacylxylidides disclosed andclaimed herein with the biotoxins, tetrodotoxin or saxitoxin. It will benoted that the herein claim aminoaeylxylidides have the distinctadvantage, in combination with such biotoxins, of providing anaestheticshaving unusually long nerveblocking effect.

TABLE X (min. quency 126 i 12 157 1: 18 295** 420 min.*** 24 hrs. 420min. 24 hrs. 128 i 13 133 i 316 i 10** 420 min. 24 hrs. 420 min. 24 hrs.97 i 4 TTX TTX TTX 1.0 3

TTX 1 TTX, 0.25

TTX 0.5 l

STX

STX 420 min.

24 hrs. 420 min. 24 hrs.

STX 1.0 2

Footnotes for Table X *For test method. see Table 1. One animal blocked420 min. 5 *The notation 420 min. 24 hrs. means that the animalsrecovered during a period when they were not observed.

The test solution of compounds A and B contained epinephrine in a conecntration 11100000.

The effect of compositions of compounds D and E, respectively, withtetrodotoxin (TTX) was also evaluated by tests on frog sciatic nerves.The pH of the tests was 5.6 and the method used is described below.

Compound D and TTX alone gave 24 and 29 reduction, respectively, in theaction potential, whereas the combination of the two in the sameconcentrations reduced such potential by 94%. In the case of compound E,the reduction in the potential produced by the combination was 94%, ascompared with 22 and 15%, respectively, for compounds E and TTX alone.There is, therefore, a decidedadvantage in the combination of the twodrugs as compared with the individual compounds. (See Table X1).

TABLE x1 Effect of the presence of compounds D and E on Tetrodotoxin(TTX) blocks of isolated intact frog sciatic nerve at pH 5.6.

*The numbers in parenthesis indicate the range observed in theexperiments **An occasional high value is sometimes observed. Thelogical explanation for this is some minute injury done to the nervesheath during dissection. It takes about 50 times the concentration ofTTX necessary to block a desheathed nerve in order to obtain the samedegree of block of an intact (sheathed) nerve.

Following the procedure described above in Table VI, tests were made onthe nerve blocking effect of compounds D and E, respectively, combinedwith the biotoxin, saxitoxin, in peridural anaesthesia in the dog. Thedata obtained are presented below in Table XII. It will be noted thatcompound D alone gave a duration of block of digital pain and scrotalpain of 289 minutes and 218 minutes, respectively, whereas incombination with saxitoxin, duration of block was l-2 days for digitalpain and more than 8 hrs. for scrotal pain. Compound E in a 2% solutionproduced a duration of block of l to 2 days for digital pain and greaterthan 7% hrs. for scrotal pain. All animals recovered completely.

TABLE XII Peridural Anaesthesia in dog with compounds D and E added toSaxitoxin (STX) solutions. STX 4 ug/ml. Volume 5 m1.

Drug Duration of block of Digital Scrotal (concn.) Pain Pain D 1% l-2days 480 min.

24 hrs. E 2% l-2 days 420 min.

24 hrs.

Epinephrine l:l00,000 used in all solutions.

Method: See Table VI.

Note:

A volume of 10 m1. 1% solution of Compound D gave durations of block ofdigital pain and scrotal pain of 289 min. and 218 minutes respectively(Table VI).

Compound D was also tested alone and in combination with Saxitoxin (STX)in spinal anaesthesia in sheep. The results and the procedure followedare described in Table XIII below. It is significant that, particularlyin the case of digital pain, the addition of compound D to Saxitoxinincreased the duration of block from about 69 to about 267, an increaseof about 3% fold.

The solutions contained 7.57: dextrose (pH 4.0). One ml. wasadministered in each experiment. The sheep (23-29 kg.) were restrainedin the horizontal position during the injection and then immediatelytilted so that the slope of the spine was positioned ten degrees to thehorizontal plane (caudal inferior). The administration was performedbetween I.6-S1 and was made with 22 gauge three inch disposable needlesusing the socalled lateral rather than the midline approach,

Note: I

Compound D alone in a concentration 01' 171, i.e.. four times theconcentration used in the experiments summarized above, provided aduration of block of digital pain that lasted for 45 61) min. with anonset time of 5-10 minutes.

Compounds D and E were tested for their effect on the brain and thespinal cord in the peridural cat following the procedure described inTable III above. Compound D was tested in 1% concentration and compoundE in 2% concentration. Following the tests the brain and the entirespinal cord were examined and no pathological change attributable to thedrugs was found.

The results reported in the preceding tables on the in vitro studies onfrog sciatic nerve were obtained by use of the following method,essentially as described by A. P. Truant, Arch. Int. Pharmacodyn. 115:483497 (1958):

Sciatic nerve trunks of Rana pipiens are prepared by dissecting thenerve from its roots in the spinal cord to the ankle and placing it onsilver silver chloride electrodes so that stimulation and recording canbe performed during the course of application of the test compounds andduring the recovery period. The bathing solution is Tasaki Ringers, andfor each block and recovery the pI-Is of the drug solution and therecovery solution were identical.

The irritation liability of the compounds was determined according to atest procedure given in A. P. Truant, Arch. Int. Pharmacodyn. l 15:483-497 (1958). At the concentrations that are of clinical significance,compounds C and D were not more irritating than bupivacaine at 0.5%concentration.

The test method employed for the acute toxicity studies reported inTable V was as follows:

Sexually mature female animals are used.

Animals are divided into groups of and dosed with drug solution orvehicle. After being dosed, animals are observed at intervals forseveral hours for overt effects and fatalities. Survivors are housed asgroups according to dose level and checked once daily for the durationof the study in order to determine whether or not delayed fatalitiesoccur.

LD s and 95% Fieller confidence limits (or 95% approximate limits) arecalculated by the Minimum Lo git Chi Square Method of Berkson, J. Am.Stat. Assoc. 48: 565 (1953).

The tertiary-amylamino-acetoxylidide compounds of the invention(compounds C and D) have unusual, long-lasting local anaesthetic effectand high local an- 18 aesthetic activity, satisfactory low level oftissue irritation and satisfactory low acute toxicity compared withbupivacaine (compound X). The tertiary-butylaminoacetoxylidide compoundof the invention (compound A) has an unusually longlasting localanaesthetic effect and an unusually low intravenous toxicity compared toits structural isomer lidocaine (compound Y). Its tissue irritationliability is also quite satisfactory.

Generally, the compounds of the invention will be used in 0.252% watersolution with or without addition of a vasoconstrictor in infiltrationanaesthesia, peridural and subarachnoid anaesthesia. Their use is,however, not restricted to this concentration range and the ,dose andconcentration used must be determined in @each case with considerationgiven to such factors as the age and body weight of the patient, as wellas to the route of administration, and the clinical anaestheticrequirements. The compounds of the invention can also be appliedtopically to mucous membranes and damaged, e.g., abraided, skin in theform of solutions, ointments, jellies, or aerosols. Examples of suitablepharmaceutical compositions which may be used as local anaesthetics aregiven in Table VIII, using compound D as the active ingredient. Similarcompositions, using. compounds A, B, C, E or F as the active ingredientmay be formulated in a manner known in the art, possibly adjusting theNaCl content to obtain isotonicity.

We claim:

1. A local anesthetic compound selected from the group consisting of2-(N-ethyl-tert.-amylamino)-2,6- acetoxylidide and a pharmaceuticallyacceptable salt thereof.

2. A local anesthetic compound selected from the group consisting of2-(N-n-propyl-tert.-amylamino)- 2' ,6-acetoxylidide and apharmaceutically acceptable salt thereof. 1

3. A local anesthetic compound selected from the group consisting ofZ-(N-n-butyl-tert.-butylamino)-2,- 6-acetoxylidide and apharmaceutically acceptable salt thereof.

4. A local anesthetic compound selected from the group consisting of2-(N-tert.-amylamino)-2',6- acetoxylidide and a pharmaceuticallyacceptable salt thereof.

UNITED STATES PATENT AND TRADEMARK OFFICE @ER'HHCATE OF CURRECTIQNPATENT NO. 3,925,469 DATED December 9, 1975 INV ENTOR(S) Herbert J. F.Adams et al It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:7

First page of patent, after the caption "Inventors: "Herbert H, F.Adams, Westboro; Jon C. Anderson, Wyckoff, both of N.J. should readHerbert J. F. Adams, Westboro, Mass. Jon C. Anderson, Wyckoff, N.J. Col.5, line 48, il tsert B. Col. 7 line 4, "cmshould read cm Col. 8, line36, "until more" should read until no more Col. 9, line 12, before"white" insert a line 65, before "white" insert a Col. 10, line 54,"butylaminol should read butylamino line 62, "N-propy-tert.amylamine"should read N-propyltert.amylamine Col. 11,

line 33, 2-tert.butylamino) 2' ,6 acetoxylidide" should read 2-(tert.butylamino) 2' ,6'acetoxylidide Col. 12, line 18, "the local"should read these local Col. 13, line 12, "579-58" should read 579-587.Col. 14, line 5 of Table VIII, the caption "0.25%" should read 0.25%*Col, 15, line 10, "369,202" should read 369,302

line 21, "claim" should read claimed Signed and Sealed this twenty-fifthDay Of May 1976 {SEAL} Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'Parenlsand Trademarks

1. A LOCAL ANESTHETIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF2-(N-ETHYL-TERT.-AMYLAMINO)-2''-,6'',ACETOXYLIDIDE AND APHARMACEUTICALLY ACCEPTABLE SALT THEREOF.
 2. A local anesthetic compoundselected from the group consisting of 2-(N-n-propyl-tert.-amylamino)-2'',6''-acetoxylidide and a pharmaceutically acceptable salt thereof.
 3. Alocal anesthetic compound selected from the group consisting of2-(N-n-butyl-tert.-butylamino)-2'' ,6''-acetoxylidide and apharmaceutically acceptable salt thereOf.
 4. A local anesthetic compoundselected from the group consisting of 2-(N-tert.-amylamino)-2'',6''-acetoxylidide and a pharmaceutically acceptable salt thereof.